Screw-cutting lathe



s. H. VARNDELL SCREW I CUTTING LATfiE Filed 001;. .28, 1943 Aug. 7, 1945.

5 Sheets- Sheet 1 Y Inventor SYDNEY HVARNDELL A ttorn ey s. H. VARNDELI,

SCREW CUTTING LATHE Filed Oct. 28, 194:

5 sheets-sheet 2 Inventor v Sypmsv H. VARNDELL.

Attorny Aug. 7, s H. VARNDELL 2,381,849

SCREW CUTTING LAT HE Filed Oct. 28, 1943 5'SheetsSheet 3 I I v I 'Ir wenlor SYDNEY, H. VA Ripe; L

A ttorney I I Y Patented Aug. 7, 1945 I I pplication October 2 j, {claim T This invention comprises -improvements con nec'te' d with *screw cuttinglathesof 1 the type which are adapted -for"c-hasing threadsythe' mas- 'fter" thread being on; a former onthe lathe. I

de an improved arrangement? whereby the trav'el {iii-the segmental nut *part -or'-- the like along the thread on the former *t'ogetherjwith the thread cutting tool is automatically stopped at a predetermined position, thereby-*-elim inat-, ing the -risk tof the tool over running the requisite 1 3 -I Ii vide ari-';"in'1plroved arrangement for the*mount- I ing -of the: segmental n'utpr the like which' is a'dapted to engage the"screwed formen'the screwzcutting tool and the operating handleforcontrol1ing the'beforementioned parts. I h

- =R'eferring-:to*thei drawings+- ji 1 Fiaur'e =1- is a I Hunt-elevation f, ascrew cut-v -.;;ting 1athe, according tothisinvention? r 1 n .1' .I v- Figures isfan-er'idble'vatioh.=

iv 'Figur'ed is a' section--at-4'- '4fin Figur of I II I I is secured to" the tubu1ar1part 25'by being passed through a=ho1e insaid{tubular-part'-25 and then -:the operating lever,whilst; I I I Figure 5 i's a demo-section of the-arrangement efor mountinglthe screwed former.""' I I I Inz-carr'ying the present invention intopra-c- :tice; as shown upon' the 'aiccom'pa-nyingdrawings, tat the rear of theiathe spindle 'Pis mounted a spindle 8 to which a screwed"'former--9-'is"con- -nected,-'::said ispindle iscarriedby a bush I0 mounted inithel lathe frame I I -This bush l 0 I being held in; thezframe I I by the fixing screw The :screwed former 9 has formed on same an xtension I 3; which: is positioned in a recess I 4 f locking screw 15. a

a .1'Tofliremove the screwed #former- 9 to change same, the locking screw I2 holding the-bush"-I0 intpositiom in the lathe frame -I I' -is unloosened to permit "ofthe bush in being vwithdraw' to- [gether with the spindle 8 and-the screwed former' 9 with it,- whilst by unloosening thelocking screw I5 in the, spindle 8 which secures the screwed former 9 to said spindle 8, the screwed former 9 can be removed and changed. I

The screwed 'former 9 is driven bya train of gears. I9 ofith'e lathe spindle 1, so that the speed of. the screwed former 9'is half that of the lathe I spindle I. I

Positioned over the screwed former 9 is a tubular part I! which forms part of the member I8. The tubular part I! of themember l8 -The' object of the presentinvention is to 'pr'o- A'-- fur-ther' object of' this invention is to -pror n: the" spindle 8i andis secured fto same by a s'osmw-oor'rmc LATHE I r ihfi nen iwarh en mien enema" z 8, 1943-; seria1 tie- 507333 I E 2 l M v- I a -ismounted inthe frame II- ofthe lathe; whilst the-opposite endof the=member *-I 8 is secured Mounted within the' -tubular part' I'I of-the j -member- I 8 is abe'airi-ng in which is mounted *the spigot H on the end of-the screwed-former 9. The top of the-tubu1ar-part I I -'I' in' alignment with the'-'screwed-' former 9-has a slot"22- cut thereinto accommodate the 'segmental 'portion -of a nut="23,-*which'cohtrols -the traveliof the '-thread cutting'too1 24'.--

Mounted over the beforementioned member I8is a tubularpart fi which at each end is ;15 mountedon distance pieces; which are slidably *mounted on the "member 48, whilst in thespace 1 between the '-member'- I 8 and the tubular partf25 is disposed a tension'spring w;the%one. end'of a; which" is-"connected-to the member I B "--byinserting the bentoverend of the spring- 50 in a hole in the I member I 8 and securing same '-in'- posi-' .-tion=by means of the screw 5I. A hole-52 is cut in the tubu1ar part'25 toobtain' ac'cess to the screw--5I.-The opposite endof' the spring{ 50 I bent over onto-same,"

Rotatably-mounted eh- 'the tubular part 2s is ,35 nectedmembers-29 30. --The first of'these mem- :-'bers'=,' '29 issec'uredto .the beforementioned tubu- -lar part' 25; whilst the second of said members,

-39 is pivotallymountedat'3I in the side members 26, 21 and has a toothed part '32 on its 40 inner-en'd whichis adapted toengage 'a complementary :part 33 -in the member"-29 secured to athe tubular part 25; l v

The outer end 3i of said pivoted member 30 is adapted to engage the adjustable bar 35. which is secured to the front of the lathe head,'which bar 35, can be adjusted to'the required depth of the thread to be cut and also to the taper if a tapered part is to be threaded, by means of the adjusting screws 42, 43 and 44: In this bar 35 'is provided a gap 36, so that on the arm advancing along the bar 35 and the pivoted memc In operation, the pivoted arm carrying the segmental nut, part 23 and the thread cutting tool 24 are normally turned up so that they are disposed substantially vertically at the back of the lathe. When it is desired to chase a thread, the pivoted arm is brought down by means of the handle 28 until the outer'end 34 of the pivotally mounted member 30 disposed in the arm, is brought into engagement with the adjustable bar 35 mounted on the front of the lathe head.

This downward pressure is maintained by the operator on the handle 28 during the thread cutting operation. The downward pressure exerted on the handle 28 is such that. the hardened stop member 49, secured to the end of the member 21 of the pivoted arm is brought into contact with the adjustable bar 35 along whichthe pivoted arm 26,,21 travels during the thread cutting-operation. The pivotally mounted member 38, will cause the interconnected member 29 in said arm, to swing and partially rotate with it the tubular part 25, towhich is connected the tool arm 3'! and bring the threadvcutting tool 24 into position for cutting a thread. Simultaneously with this movement, the segmental portion of the nut 23. which is adapted to engage the threaded former 9 and which is connected to the arm 39- of the member 30 pivotally mounted .at 3|, is moved into engagement with the threadediormer 9 1 The thread .cutting tool 24 will now travel along together with thearm in which the handle 28 is mounted until-the.-, ap 36 is reached in the bar 35 positioned on the front of the lathe head, which is engaged by the end34 of the pivoted interconnected part 30 in the arm. When this gap.36 is reached the pivoted member 30, under the action of thesprings MIv connected to the pin 48 mounted in the member 29. and to the members 26, 21, automatically falls and I causes the segmental .nuttpart 23 to,disengage the threaded former 9 and the thread cuttingv tool 24 to be raised to disengage the work in the lathe chuck 45, thus automatically stopping the travel of the pivoted arm, which is retained on the bar35 and does not fall at the gap 36, only the end; 34. of the pivoted member 30 entering the gap.36 as at this moment the segmental ;nut part 23 disengages the screwed former 9 and the travel of the hand1ef28 is automatically, stopped. p

At this point, the tension spring 50 which is disposed between the member [8 and the tubular part 25 will have been-extendedduring the holder is broughttravel of the tubular part 25 along the member l8, whilst at the same time torsion will also have been imparted to said spring by the rotation of the arm from its normal vertical position to its thread cutting position. On the handle 28 of the arm being released, the arm will return automatically to its normal vertical position and be returned back along the member I8 to its normal position by the spring 50.

An adjustable collar 4| is preferably mounted on "the member l8 to set the initial position of the thread cutting tool 24 and with it the tubular ,member pivotally mounted in said lever to which a former engaging member is connected, a member pivotally mounted in said lever and interconnected with the control member which is connected with a thread cutting tool holder, and

an abutment against which said control member is adapted to abut, so that on said control member being brought into engagement with the abutment and pressure exerted on said lever,

the former engaging member isbrought into engagement with the screwed former and the tool into position for cutting a screwthread.

2. Improvements in screw-cutting lathes, comprising in combination, a screwed former, a

traversing and pivotally mounted lever, a control member pivotally mounted in said lever to which a former engaging member is connected, a member pivotally mounted in said lever and interconnected with the control member which is connected .Witha thread cutting tool holder, an abutment against which said control member is adapted to abut, a gap in said abutment, so that on said control member being brought into engagement with the abutment and pressure exerted on said lever the former engaging member is brought into engagement with the. screwed former and the tool holder is brought into position for cutting a, screw thread, whilst when the control memberreaches the gap in the abut- H ment, pressure is released on same and the former engaging member automatically disengages, the screwed former and the thread cutting tool the work. v e

3. Improvements, in screw-cutting lathes, comprising in combination, a screwed former, a guide member, a lever pivotally mounted on said guide member, an extension on said lever on which a tool holder is mounted; a, control member pivotally mountedin'said lever to which a former 

